1. Field of the Invention
The invention relates to a gypsum moldings as building materials and methods manufacturing the said gypsum moldings by use of fibrous .alpha.-calcium sulfate hemihydrate as a raw material.
More particularly, the invention relates to a gypsum moldings as building materials having desired specific gravity and desired bending strength.
Farthermore, the invention relates to methods manufacturing the said gypsum moldings.
The said moldings of the invention is very useful as building materials because of its noncombustibility and high strength.
2. Description of the Prior Arts
The gypsum moldings essentially consists of calcium sulfate dihydrate, and hitherto has been manufactured by either of the following two methods.
One of them essentially consists of firing fibrous .alpha.-calcium sulfate hemihydrate as a raw material, molding the resulting fibrous calcium sulfate anhydride, curing and drying the resulting moldings.
The other essentially consists of mixing powdered .beta.-calcium sulfate hemihydrate as a raw material with a suitable amount of water, papering and dehydrating the resulting paste, molding the resulting wet mat, and then curing and drying the resulting moldings to convert .beta.-calcium sulfate hemihydrate into dihydrate.
The former essentially includes the process converting fibrous .alpha.-calcium sulfate hemihydrate into fibrous anhydride, so enormous energy is necessary to the dehydration process.
The latter has a fault of giving only moldings of limited specific gravity, because in this method it is necessary to limit the amount of water with which .beta.-calcium sulfate hemihydrate is mixed.